Vacuum filtration is commonly used in the manufacture of a variety of agricultural, food, beverage, and biotechnology industries. In addition to the fixed equipment, production scale vacuum filtration systems such as rotary drum vacuum filters, leaf filters, and the like typically employ process aids, which are also referred to as filtration aids. These consumable aids range from fibers, cloths, and the like to particle materials such as clays, diatomaceous earth, carbon, cellulosics and associated materials and are used to coat the filters. These materials retain both insoluble and soluble impurities by various physicochemical means. Particulate materials are also sometimes added to the prefiltration supernatants and subsequently recovered from the filter as a high moisture filter cake as it accumulates on the filter surface. A number of permutations of this approach are practiced in an array of industries today. For example, diatomaceous earth (DE) is a widely used filter medium. Diatomaceous earth is frequently used, alone or in conjunction with other process aids, to clarify water, beverages including beers, wines, juices and the like, and also to clarify food ingredients such as maltodextrins, syrups and the like.
An undesirable and problematic aspect of filtration systems that employ a filtration aid is the disposal of the used (spent) filtration aid. Because of the significant cost and time entailed in the recycling of filtration aids, generally the spent filter media is simply disposed of in a landfill. However, disposing of this media in a landfill is wasteful and unproductive.
Materials that can be used in filtering aids often have other functionalities and utilities. Diatomaceous earth also is widely used in gardening, landscaping, and potting soil mixes. Diatomaceous earth also is used as a non-toxic, organic insecticide, where it is regarded as a safe alternative to chemical insecticides. For these applications, the diatomaceous earth is typically added as a dry mined powder. The diatomaceous earth is typically added to the final gardening, landscaping, and potting soil mix and dry blended. In these applications, the diatomaceous earth typically is devoid of biomolecules such as carbohydrates and proteins or other extraneous matter.
Diatomaceous earth found in spent filter media is generally not suitable in such lawn and garden applications. The spent filter media contains a significant amount of water, and generally also contains particulates and other material such as carbon and nutrients retained from the filtration stream. If the filter media is not dried or preserved immediately, uncontrolled microbial growth can occur in the presence of the media. Such microbial growth generally will render the media unsuitable for lawn and garden applications. Diatomaceous earth may be dried, but known drying processes are deemed to be uneconomical in lawn and garden applications. Moreover, organic material entrapped in the diatomaceous earth often is undesirable. For example, organics are deemed undesired in potting soil mixes and seed bedding soils.
Other approaches such as composting (as purportedly disclosed in U.S. Pat. No. 6,261,604) have been suggested, but these approaches have not been widely adapted. Composting is a slow, laborious process that requires substantial time and space. Moreover, although composting does address some broad disposal issues, composting does not significantly enhance the utility of the media.
Thus, the absence of a technology to efficiently recycle spent filter media reduces its value and causes users to incur disposal expense.